Discouraged by Object-Oriented Programming, Many mixed languages support it. And developers abuse them.

TL;DR: Global functions bring a lot of coupling. Don't use them.

Problems

• Coupling

• Readability

• Maintainability

• Testability

Solutions

• Wrap the function in a context object.

Examples

• External Resources Access, Database access, Time and Operating System resources.

Sample Code

Wrong

<?

class Employee {
    function taxesPayedUntilToday() {
        return database()->select(
            "SELECT TAXES FROM EMPLOYEE".
            " WHERE ID = " . $this->id() .
            " AND DATE < " . currentDate());
    }
}

Right

<?

final class EmployeeTaxesCalculator {
    function taxesPayedUntilToday($context) {
        return $context->SelectTaxesForEmployeeUntil(
            $this->ssn,
            $context->currentDate());
    }
}

Detection

Many modern languages avoid them. For the permissive ones, scope rules can be applied and automatically checked.

Tags

• Global

Conclusion

Structured programming considers global functions harmful. Yet, we can observe some bad practices cross paradigm boundaries.

Relations

• Singleton and Classes are global points of access.

More Info

• Wikipedia

Credits

Photo by Mae Mu on Unsplash

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The road to programming hell is paved with global variables.

Steve McConnell

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This article is part of the CodeSmell Series.

Last update: 2021/06/26